Answer:
What occurs once in a minute, twice in a moment and never in one thousand years?
What do you have in December that you don't have in any other month?
There is one in every corner and two in every room.
Environmentalists want to keep this from drying.
Sitting down you have it, Standing up you don't.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.